ITS SUBTF.RRANKAN MODIFICATIONS. 105 



bud or branch in its axil (as in the Barberry, Fig. 296), it must be 

 of the nature of a leaf. 

 187. The Subterranean Modifications of the Stem are scarcely less 



numerous and diverse than the aerial ; but they may all be reduced 

 to a few principal types. They are perfectly distinguishable from 

 roots by producing regular buds, or by being marked with scars, 

 which indicate the former insertion of leaves, or furnished with 

 scales, which are the rudiments or the vestiges of leaves. All the 

 Scaly roots of the older botanists are therefore forms of the stem or 

 branches, with which they accord in every essential respect. So, 

 likewise, what are popularly called Creeping roots are really subter- 

 ranean branches ; such as those of the Mint, and of most Sedges and 

 Grasses. Some of these, such as the Carex arenaria (Fig. 1GG) of 



Europe, render important service in binding the shifting sands of 

 the sea-shore. Others, like the Couch-Grass, are often very trouble- 

 some to the agriculturist, who finds it next to impossible to destroy 

 them by the ordinary operations of husbandry ; for, being furnished 

 with buds and roots at every node, which are extremely tenacious of 

 life, when torn in pieces by the plough, each fragment is only placed 

 ^in the more favorable condition for becoming an independent plant. 

 The Nut-Grass (Cyperus Hydra), an equally troublesome pest to 

 the planters of Carolina and Georgia, is similarly constituted ; and 



FIG 166 Creeping subterranean stem of Carex arenaria. 



FIG. 167. Rhizoma of Diphyllcia cymosa, showing six years' growth, and a bud fcr the 

 seventh : a, the bud : 4, base of the stalk of the current year : c, scar left by the decay of the 

 annual stalk of the year before ; and beyond are the scars of previous } oars 



